1. Field of the Invention
The present invention relates to a lens barrier opening/closing device for opening and closing a lens barrier which is disposed in a front end of a movable lens barrel for the purpose of preventing the front surface of the lens from being stained or damaged.
2. Description of the Related Art
A zoom lens of a camera which has a movable barrel driven to advance from a housed position (accommodation position) to a photographing position when the power is turned ON is known in the art. Such a zoom lens which is provided in the front end thereof with a lens barrier (which generally has a plurality of movable barrier blades) that is driven to open and close a forefront photographic aperture of the zoom lens by moving the movable barrel of the zoom lens from the housed position to the advance position and from the advance position to the housed position, in that order, is also known in the art.
In one of the lens barriers of this type, a barrier drive ring is provided to be rotatable about the optical axis of the zoom lens to open and close the barrier blades. The barrier drive ring is constantly biased toward one rotational end thereof to open the barrier blades by a spring. A rearward movement of the movable barrel of the zoom lens from the photographing position to the housed position causes another movable member of the zoom lens to be engaged with the barrier drive ring to rotate the same in one direction to close the barrier blades against the spring force. Conversely, a forward movement of the movable barrel of the zoom lens from the housed position to the photographing position causes the above-mentioned movable member to be disengaged from the barrier drive ring, thereby allowing the barrier drive ring to rotate in the other direction to open the barrier blades by the spring force.
In an alternative lens barriers of the aforementioned type, the barrier drive ring is constantly biased toward one rotational end thereof to open the barrier blades by a spring (first spring), while the barrier blades themselves are constantly biased in a direction to be closed by another spring or springs (second spring) whose spring force is smaller than the first spring. A rearward movement of the movable barrel of the zoom lens from the photographing position to the housed position causes another movable member of the zoom lens to be engaged with the barrier drive ring to rotate the same in one direction to restrict the spring force of the first spring, thereby allowing the barrier blades to be closed by the spring force of the second spring.
In these types of lens barriers, the barrier blades can be reliably opened and closed by a spring (biasing device) having a large spring force (large biasing force). However, the performance of the advancing/retreating operation of the movable barrel of the zoom lens, which moves between the housed position and the photographing position, deteriorates if the spring force is excessively large. This is because the driving force generated by a movement of the movable barrel between the housed position and the photographing position to drive the barrier blades is originally used to make the movable barrel itself advance to the photographing position or retreat to the housed position.
The difference between the photographing position and the housed position of the movable barrel can be regarded as the difference between two axial positions (two separate positions on the optical axis of the zoom lens) of the movable barrel, so that the barrier drive ring can be rotated by converting a linear movement of a movable member in the optical axis direction into a rotational movement about the optical axis. For instance, in a conventional lens barrier opening/closing device, a linearly movable barrel which moves in the direction of the optical axis without rotating about the optical axis is provided with an inclined surface which is inclined with respect to the direction of the optical axis, while the barrier drive ring is provided with another inclined surface which is inclined with respect to the direction of the optical axis. When the linearly movable barrel moves in the direction of the optical axis toward the barrier drive ring, the inclined surface of the linearly movable barrel is engaged with the inclined surface of the barrier drive ring which is pushed in the same direction, which causes the barrier drive ring to rotate about the optical axis. However, according to this structure, such an operation of converting a driving force in the direction of the optical axis into a rotational driving force about the optical axis results in a large energy loss. Accordingly, although the spring (biasing device) that biases the barrier blades preferably has a large spring force to reliably open and close as mentioned above, the performance of the advancing/retreating operation of the movable barrel of the zoom lens may deteriorate due to the large spring force since energy loss in an operation of transmitting a driving force from the linear movable member to the barrier drive is large. If the driving force for moving the movable barrel in the direction of the optical axis is increased to prevent this from occurring, an excessive load is exerted on a drive motor which drives the movable barrel.
There is further problem in such lens barrier opening/closing devices in which the barrier blades are opened and closed by rotation of the barrier drive ring. Namely, the lens barrier may not function properly if the rotational center of the barrier drive ring is eccentric from a predetermined position (generally the optical axis of the photographic optical system of the zoom lens). For instance, if the lens barrier is provided with a pair of barrier blades which are respectively pivoted at a pair of pivots fixed at different positions in a circumference of the lens barrier so that each barrier blade rotates about the corresponding pivot to be opened and closed, and if the barrier drive ring is provided thereon with a pair of engaging portions which can be respectively engaged with and disengaged from the pair of barrier blades, the pair of engaging portions of the barrier drive ring cannot be respectively engaged with and/or disengaged from the pair of barrier blades properly if the rotational center of the barrier drive ring is eccentric relative to the predetermined position. In this case, one of the pair of barrier blades may not be completely closed when the zoom lens retreats to the housed position, and/or may not be completely opened when the zoom lens advances to the photographing position.
The present invention has been devised in view of the matters mentioned above, and accordingly, an object of the present invention is to provide a lens barrier opening/closing device with which the lens barrier operates with reliability without deteriorating the operational performance of the movable lens barrel.
Another object of the present invention is to provide a lens barrier opening/closing apparatus which prevents the rotational center of the barrier drive ring from being eccentric from the optical axis of the photographic optical axis so that the lens barrier operates reliably. Other objects of the invention will become apparent to one skilled in the art from the following disclosure and the appended claims.
To achieve the object mentioned above, according to an aspect of the present invention, a lens barrier opening/closing device of a movable lens barrel driven to move between an accommodation position and a photographing position is provided, including at least one barrier blade which is driven to open and close a photographic aperture formed at the front end wall of the movable lens barrel when the movable lens barrel is in the photographing position and the accommodation position, respectively; a barrier drive ring driven to rotate about an optical axis to drive the barrier blade; a first biasing device which biases the barrier drive ring in a predetermined rotational direction; a rotational barrel which at least rotates about the optical axis when the movable lens barrel moves between the accommodation position and the photographing position; a rotational-force receiving surface formed on the barrier drive ring, which extends parallel to the optical axis; and a rotational-force transmission surface formed on the rotational barrel, which extends parallel to the optical axis. The rotational-force receiving surface and the rotational-force transmission surface are engaged with each other to rotate the barrier drive ring together with the rotational barrel about the optical axis in a direction against a biasing force of the first biasing device when the movable lens barrel moves from one of the photographing position and the accommodation position to the other of the photographing position and the accommodation position.
Preferably, the barrier drive ring includes a drive lever which extends substantially parallel to the optical axis toward the rotational barrel, the drive lever including the rotational-force receiving surface thereon.
Preferably, the rotational barrel includes a recess formed to allow the drive lever to enter the recess, the rotational-force transmission surface being formed as a wall of the recess.
The movable lens barrel can be an element of a zoom lens of a camera.
Preferably, the first biasing device includes at least one helical extension spring.
In an embodiment, the barrier drive ring and the rotational barrel rotate relative to each other about the optical axis and move relative to each other in a direction of the optical axis when the movable lens barrel moves between the photographing position and the accommodation position. The barrier drive ring and the rotational barrel are apart from each other so that the rotational-force receiving surface and the rotational-force transmission surface do not overlap each other in the direction of the optical axis when the movable lens barrel is in a specific one of the photographing position and the accommodation position in which the rotational barrel does not drive the barrier drive ring to rotate about the optical axis via the rotational-force receiving surface and the rotational-force transmission surface.
In an embodiment, the lens barrier opening/closing device further includes a linearly movable barrel positioned around the rotational barrel, guided in the direction of the optical axis without rotating about the optical axis, and supporting the barrier drive ring in a front end of the linearly movable barrel so that the barrier drive ring is rotatable about the optical axis; a radially inward pin formed on the linearly movable barrel to extend radially inwards; and a guide groove, corresponding to the radially inward pin, formed on an outer peripheral surface of the rotational barrel to be engaged with the radially inward pin to move the linearly movable barrel in the direction of the optical axis by rotation of the rotational barrel.
Preferably, the movable lens barrel is an element of a zoom lens of a camera, and the linearly movable barrel functions as a movable lens hood which advances relative to the rotational barrel when the zoom lens is set at a telephoto extremity thereof having a narrow angle of view, and which retreats relative to the rotational barrel when the zoom lens is set at a wide-angle extremity thereof having a wide angle of view.
In an embodiment, the lens barrier opening/closing device further includes a second biasing device which biases the barrier blade in a direction toward one of an open position and a closed position of the barrier blade against the biasing force of the first biasing device, a biasing force of the second biasing device being smaller than that of the first biasing device. The barrier blade is driven by the biasing force of the second biasing device when the barrier drive ring is driven to rotate against the biasing force of the first biasing device by rotation of the rotational barrel.
Preferably, the second biasing device includes at least one torsion spring.
According to another aspect of the present invention, a lens barrier opening/closing device of a movable lens barrel is provided, including at least one barrier blade which is driven to open and close a photographic aperture formed at the front of the movable lens barrel; a rotational barrel which at least rotates about an optical axis when the movable lens barrel moves between an accommodation position and a photographing position; a barrier drive ring driven to rotate about the optical axis to drive the barrier blade; an opening biasing device which biases the barrier drive ring in a direction to open the barrier blade; a rotational-force receiving surface formed on the barrier drive ring to extend parallel to the optical axis; and a rotational-force transmission surface formed on the rotational barrel to extend parallel to the optical axis. The rotational-force receiving surface and the rotational-force transmission surface are engaged with each other to rotate the barrier drive ring about the optical axis in a direction to close the barrier blade against the biasing force of the opening biasing device while the rotational barrel rotates when the movable lens barrel moves from the photographing position to the accommodation position.
In an embodiment, the lens barrier opening/closing device further includes a linearly movable barrel guided in a direction of the optical axis without rotating about the optical axis, the linearly movable barrel supporting the barrier drive ring at a front end thereof so that the barrier drive ring is rotatable about the optical axis.
In an embodiment, the lens barrier opening/closing device further includes at least one engaging portion formed on the barrier drive ring to be engageable with the barrier blade; and a closing biasing device which biases the barrier blade in a direction to close the photographic aperture, a biasing force of the closing biasing device being smaller than that of the opening biasing device. The engaging portion of the barrier drive ring held at a position to open the barrier blade by the biasing force of the opening biasing device pushes the barrier blade to open the barrier blade when the movable lens barrel is in the photographing position. The engaging portion is disengaged from the barrier blade so that the barrier blade is driven to be closed by the biasing force of the closing biasing device when the barrier drive ring is driven to rotate about the optical axis against the biasing force of the opening biasing device by rotation of the rotational barrel when the movable lens barrel moves from the photographing position to the accommodation position.
According to another aspect of the present invention, a camera is provided, including a movable lens barrel driven to move between a photographing position an accommodation position when the power of the camera is turned ON and OFF, respectively; at least one barrier blade driven to open and close a photographic aperture formed at the front of the movable lens barrel when the movable lens barrel is in the photographing position and the accommodation position, respectively; a barrier drive ring driven to rotate about an optical axis to drive the barrier blade; at least one spring which biases the barrier drive ring in a direction to open the barrier blade; a rotational barrel which rotates about the optical axis when the movable lens barrel moves between the accommodation position and the photographing position; a lever formed on the barrier drive ring to extend toward the rotational barrel, the lever including a first engaging surface extending parallel to the optical axis; and a recess formed on the rotational barrel so that the lever can enter the recess in a direction of the optical axis, the recess including a second engaging surface extending parallel to the optical axis. The first engaging surface and the second engaging surface are engaged with each other to rotate the barrier drive ring about the optical axis in a direction to close the barrier blade against the biasing force of the biasing device when the movable lens barrel moves from the photographing position to the accommodation position.
According to another aspect of the present invention a lens barrier opening/closing device of a movable lens barrel driven to move between an accommodation position and a photographing position is provided, including at least one barrier blade which is driven to open and close a photographic aperture formed at the front of the movable lens barrel when the movable lens barrel is in the photographing position and the accommodation position, respectively; a linearly movable barrel guided in a direction of an optical axis without rotating about the optical axis; a barrier drive ring driven to rotate about the optical axis to drive the barrier blade, the linearly movable barrel supporting the barrier drive ring in a front end of the linearly movable barrel to be rotatable about the optical axis; and a pair of ring biasing springs positioned between the barrier drive ring and the linearly movable barrel on opposite sides with respect to the optical axis in a radial direction to bias the barrier drive ring in a predetermined rotational direction. The barrier drive ring is driven to rotate in a rotational direction opposite to the predetermined rotational direction against a biasing force of the pair of ring biasing springs by a movement of a movable member provided in the lens barrel when the movable lens barrel moves from one of the photographing position and the accommodation position to the other of the photographing position and the accommodation position.
In an embodiment, the lens barrier opening/closing device further includes at least one barrier biasing spring which biases the barrier blade in a direction opposite to a biasing direction of the pair of ring biasing springs toward one of an open position and a closed position of the barrier blade, wherein a biasing force of the barrier biasing spring is smaller than that of the pair of ring biasing springs, and wherein the barrier blade is driven by the biasing force of the barrier biasing spring to move to one of the open position and the closed position when the barrier drive ring is driven to rotate against the biasing force of the pair of ring biasing springs.
In an embodiment, the barrier blade includes at least one pair of barrier blades; the barrier biasing spring includes a pair of barrier biasing springs positioned on opposite sides with respect to the optical axis in the radial direction to bias each of the at least one pair of barrier blades toward one of the open position and the closed position; the barrier drive ring includes at least one pair of engaging portions which can be engaged with the at least one pair of barrier blades, respectively. The barrier drive ring is engaged with at least one pair of the barrier blades to push the at least one pair of barrier blades via the at least one pair of engaging portions against a biasing force of the pair of barrier biasing springs when driven to rotate about the optical axis in the predetermined rotational direction. The barrier drive ring is disengaged from the at least one pair of barrier blades when driven to rotate about the optical axis against a biasing force of the pair of ring biasing springs via the movement of the movable member.
In an embodiment, the linearly movable barrel includes a pair of first protrusions positioned on opposite sides with respect to the optical axis in the radial direction, the barrier drive ring includes a pair of second protrusions positioned on opposite sides with respect to the optical axis in the radial direction, the pair of ring biasing springs are formed as two helical extension springs, and the opposite ends of one of the two helical extension springs are connected to one of the pair of first protrusions and one of the pair of second protrusions, respectively, while the opposite ends of the other of the two helical extension springs are connected to the other of the pair of first protrusions and the other of the pair of second protrusions, respectively.
In an embodiment, the pair of ring biasing springs bias the barrier drive ring in a first rotational direction to drive the barrier blade to open the photographic aperture, and the barrier drive ring is driven to rotate in a second rotational direction opposite to the first rotational direction to drive the barrier blade to close the photographic aperture when the movable lens barrel moves from the photographing position to the accommodation position.
Preferably, the barrier biasing spring includes at least one torsion spring.
Preferably, the movable lens barrel is an element of a zoom lens of a camera.
In an embodiment, the linearly movable barrel functions as a movable lens hood which advances relative to the rotational barrel when-the zoom lens is set at a telephoto extremity thereof having a narrow angle of view, and which retreats relative to the rotational barrel when the zoom lens is set at a wide-angle extremity thereof having a wide angle of view.
According to another aspect of the present invention, a camera is provided, including a movable lens barrel driven to move between a photographing position an accommodation position when the power of the camera is turned ON and OFF, respectively; at least one barrier blade driven to open and close a photographic aperture formed at the front of the movable lens barrel when the movable lens barrel is in the photographing position and the accommodation position, respectively; a linearly movable barrel guided in a direction of an optical axis without rotating about the optical axis; a barrier drive ring driven to rotate about the optical axis to drive the barrier blade, the linearly movable barrel supporting the barrier drive ring in a front end thereof so that the barrier drive ring is rotatable about the optical axis; a rotational barrel which rotates about the optical axis when the movable lens barrel moves between the accommodation position and the photographing position; and a pair of springs positioned between the barrier drive ring and the linearly movable barrel on opposite sides, with respect to the optical axis in a radial direction, to bias the barrier drive ring in a predetermined rotational direction. The barrier drive ring is driven to rotate in a rotational direction opposite to the biased rotational direction by rotation of the rotational barrel when the movable lens barrel moves from one of the photographing position and the accommodation position to the other of the photographing position and the accommodation position.
The present disclosure relates to subject matter contained in Japanese Patent Applications Nos.2000-22747 and 2000-22748 (both filed on Jan. 31, 2000) which are expressly incorporated herein by reference in their entireties.